1. Field of the Invention
The present invention relates to an imaging technique for a magnetic resonance imaging apparatus and, more particularly, to a technique used for imaging a coronary artery.
2. Description of the Related Art
A magnetic resonance imaging apparatus is an apparatus which images the chemical and physical microscopic information of a substance or is used for the observation of a chemical shift spectrum by using a phenomenon in which when a group of nuclei having a unique magnetic moment is placed in a homogenous static field, they resonantly absorb energy of an RF field that rotates at a specific frequency.
Recently, in image diagnosis using this magnetic resonance imaging apparatus, magnetic resonance coronary angiography (MRCA) using an imaging method (TrueSSFP/FISP/Balanced FFE method or the like) which uses a steady state has been frequently used. This method can visualize a coronary artery without using any contrast medium. In addition, performing imaging at a period in end-diastole at which a coronary artery stops substantially makes it possible to reduce the disturbance of image quality ground for the movement of the coronary artery. This technique can make a coronary artery to be visualized with a contrast medium and is therefore expected as a method for screening of a coronary artery or the like.
FIG. 7 is a view for explaining a scan series in conventional magnetic resonance coronary angiography (MRCA). As disclosed in, for example, Jpn. Pat. Appln. KOKAI Publication NO. 11-229571, conventional MRCA uses a method of performing imaging by detecting an R wave in an ECG waveform and starting a scan a predetermined delay time after the detection by using the R wave as a trigger, as shown in FIG. 7.
In conventional MRCA, however, even if an optimal delay time (that allows imaging immediately before the detection of the next R wave) is set at the start of imaging, since the heart rate (R-R) of a patient changes, the set condition deviates from the optical condition in actual data acquisition, resulting in a deterioration in coronary artery visualization performance.